The present invention relates to a tape cassette containing a length of magnetic recording tape suited particularly, but not exclusively, for use in a small-size portable video tape recorder for recording and/or reproducing video information. The present invention also relates to a tape transport mechanism cooperative with the tape cassette of a type referred to above and herein provided.
There is known a system wherein the capstan operatively coupled to a drive motor is forced to contact the outer peripheral surfaces of respective supply and take-up rolls of magnetic recording tape with a contact pressure between the capstan and the take-up roll being greater than that between the capstan and the supply roll to hold the magnetic recording tape under tension, so that the magnetic recording tape can be transported from the supply roll onto the take-up roll during rotation of the capstan. By utilizing this system, one can design and construct a video tape recorder.
In the known system described above, in order to generate a greater contact pressure between the capstan and the take-up roll than that provided between the capstan and the supply roll, means for generating a pressure differential is employed. The pressure differential generating means has heretofore made use of a brake band, a torque motor or a spring element. However, it has been found that the use of any one of the brake band, the torque motor and the spring element for the pressure differential generating means renders the mechanism complicated and, at the same time, requires a relatively large space for installation, thereby imposing a limitation on design and manufacture of the device as small and as compact as possible.
In view of the above, it has long been considered difficult to design and manufacture a tape cassette containing therein a pair of supply and take-up rolls of magnetic recording tape, and what has long been done is to employ a cartridge system wherein the cartridge contains only one roll of magnetic recording tape, the free end of which tape is secured to a take-up hub, built in a drive mechanism together with the capstan, by means of a length of leader tape so that, during rotation of the take-up hub together with the capstan, the magnetic recording tape can be unwound from the roll and taken up by the take-up hub.
The known cartridge system involves several disadvantages. By way of examples, when the magnetic recording tape is completely unwound from the roll, the trailing end portion of the magnetic recording tape being unwound and taken up by the take-up hub tends to become loose to such an extent that the edge of the magnetic recording tape is damaged. Accordingly, the cartridge system cannot advantageously be used in association with a small-size, portable video camera.
In any event, U.S. Pat. No. 3,526,371, patented Sept. 1, 1970, to James W. F. Blackie et al, discloses a cartridge containing spaced apart rolls of magnetic recording tape which are supported respectively by pivotable carriages within the cartridge, and a tire-lined idler roller positioned substantially intermediate between the rolls of magnetic recording tape, said carriages being biased by a biasing spring so as to pivot in a direction close towards each other with the outer perimeters of the respective rolls of magnetic recording tape held in contact with the idler roller. This U.S. patent also discloses a tape transport mechanism provided independently of the cartridge and including a motorcoupled capstan which, when the cartridge is mounted on a tape transport deck or cartridge holder, is drivingly coupled to the tire-lined idler roller with the magnetic recording tape sandwiched therebetween so that the tape can be drawn from one roll to the other during rotation of the capstan.
The pressure differential generating means employed in the above mentioned U.S. patent is provided on the side of the tape transport mechanism, particularly on the tape transport deck, and comprises a spring-biased plunger which, when and after the cartridge has been mounted on the tape transport deck, protrudes into the cartridge and urges one of the tape rolls, which then serves as a take-up roll, towards the idler roller so that the outer perimeter of the take-up roll can be pressed against the idler roller with a greater force than that provided between the supply roll and the idler roller.
The cartridge and the tape transport mechanism disclosed in the above mentioned U.S. patent involve several disadvantages. By way of example, since the spring-biased plunger must protrude into the cartridge when and so long as the cartridge is mounted on the tape transport deck, not only is skill required to achieve a correct mounting of the cartridge on the tape transport deck, but also the removal of the cartridge from the tape transport deck cannot be done easily and smoothly without difficulty.
In addition, the pressure differential generating means employed in the above mentioned U.S. patent is, though it is in the form of the spring-biased plunger, complicated in construction and bulky in size and requires a relatively large space for installation.